Bring milk to the boil, add butter and remove from heat. Leave to cool.
Place flour, salt, sugar and yeast into a large bowl, stir together and make a well in the centre. Pour in the warm milk and butter mixture into the well, add the egg.
Mix well with a spoon, then bring everything together with your hands until you have a sticky dough. Then knead the dough on a lightly floured surface until smooth and elastic.
Put the dough in a lightly oiled bowl and cover with oiled cling film. Leave in a warm place to rise for approximately 1 hour or until doubled in size.
With the dough still in the bowl add the sultanas, mixed peel, orange zest, apple and cinnamon. Knead everything into the dough, making sure it is all well distributed. Leave to rise again for another hour.
Divide the dough into 15 even pieces. Roll each piece into a smooth ball on a lightly floured work surface.
Arrange the buns on a baking tray leaving enough space for the dough to expand. Cover with a clean tea towel and set aside to prove for 1 more hour.
Heat oven to 220C. Mix the plain flour with 5 Tbsp water, to make a paste for the cross.
Spoon into a piping bag with a small nozzle attached. Pipe a line along each row of buns, then repeat in the other direction to create crosses.
Bake for 20 minutes or until golden brown.
Gently heat the apricot jam to melt, then sieve to get rid of any chunks. While still warm, brush over the top of the warm buns and leave to cool.